1. Field of the Invention
The invention relates to a bathtub overflow alarm and more particularly pertains to alerting a user to water reaching a hazardous or dangerous level within a bathtub or other container.
2. Description of the Related Art
People often do other things while waiting for a bathtub to fill in order not to waste time. Sometimes they get engrossed in a different activity and forget they started the water. Most bathtubs are equipped with drains to prevent the overflow of the water; however, that drain line or the cover over the drain line is often not large enough to allow water to go to the drain at the rate the water is entering the bathtub. Thus damage can be caused by the water overflowing the top of the bathtub. The direct damage to surrounding materials can be great but the water may also provide an environment suitable for dangerous mold and mildew or create a slipping hazard when someone finally comes to turn off the water.
American plumbing for bathtubs are installed with piping going vertically up the end of the bathtub to a height level of the overflow drain hole in the bathtub. A right angle of pipe is added to attach the plumbing to the bathtub. That piece of pipe has one or more threaded holes for attaching a fixed overflow cover plate to it and draw it up against the bathtub. At the bottom edge of the cover plate is a narrow opening for the water to evacuate the bathtub when the water level reaches that height. However, this narrow opening often limits the amount of water which can enter the piping to an amount less than that flowing into the bathtub. Thus it is possible to overflow the entire bathtub, with the overflow cover plate fully under water.
American bathtubs have three designs for the overflow cover plate. Two of them just have different screw hole configurations for mounting the cover plate to the overflow pipes. The other has a trip lever in the center with two screw holes. As noted above, the past and present overflow plumbing designs do not allow enough volume of liquid to escape from the bathtub when the bathtub is being filled with the current overflow cover plates. Furthermore, these cover plates and the evacuation areas on the sides of the cover plates may become blocked with a variety of things as well as just a buildup of hard water deposits.
There have been many attempts to solve overflowing of bathtubs in the past but have all met with problems. The majority of examples of prior art in water level alarms are devices which float in the bathtub or suction to the side. These fail for practical purposes because people do not want the device to remain in the bathtub with them while they are relaxing and so must be removable. This means that it is likely that a person will not go to the trouble of setting the device back in the bathtub each time.
There are many different type of fluid level alarms; however, none are financially feasible for the home or commercial bathtub applications. The current designs are attached to the side of bathtubs with suction cups, so they are easily removed or stolen; attached to the wall above the bathtub and get in the way of the person bathing; uses floats which can be fouled by hard water or other debris or are hard to mount; use a diaphragm switch sensitive to pressure changes, but the rubber can wear out and not react or can leak itself, or the switch itself is buoyant, which could get stuck in the drain.
Two designs address some of the problems but create new problems. U.S. Pat. No. 5,661,462 discloses a bath overflow alarm which replaces the bath drain cover and provides an audible alarm. U.S. patent application Ser. No. US2002/0047784 A1 discloses an alternative design for replacing the bath drain cover which further may provide an alarm output using a low-power radio transmitter. While these designs solve some of the prior art problems, they require specific embodiments for each particular bath drain design. This increases their cost and creates inventory problems for both the manufacturer and the retailer. It would be desirable to provide the benefits these designs provide and reduce the cost and inventory problems they create.